Research and Planning: Sound Research

I am not very confident with creating sounds to go into my trailer a this point so I am doing extra research of existing trailers, particularly focusing on when to include louder sounds and also how many different instruments or noises should be used a the same time.

At the beginning there are only two  instruments being used, creating a slow eerie noise, which builds suspense for the audience.
Louder noises begin being made both diegetic and non-diegetic and the melody stops, creating a more jumpy feel to the trailer, allowing both excitement and fear to be felt by the audience.
After a building of noises getting faster and closer together to overwhelm the victim and thrill the audience, the sound suddenly slows again.
There is then slow eerie non-diegetic voiceover and in between each piece of dialogue there is a non-diegetic sweeping sound to create a scary feeling to the trailer. While this is happening there is still a melody faintly playing underneath this.
As the dialogue stops the music continues even through sounds of screaming and people in terror.
The whole trailer ends with a shattering noise and a non-diegetic eerie noise over it too.